Script.c: fix bogus varsz detection if alignment is off

Script.c: fix bogus varsz detection if alignment is off

when putting an unref'd char variable into a script such as here:

int x;
string y;
char b;
string z;
char c[64];

the char b was assumed to be an int, so all further var lookups
became misaligned. the datadata fixup for string z was read partially
and interpreted as an int (with a value of fixup addend << 8).
that means not even the .data + X fixup was emitted, which would then
break reassembling.

this commit does the following things:
1) if current pos is a datadata fixup, we can safely say it's a
   "pointer", so size must be 4
2) all undetected variable size *must* default to 1 rather than 4.
   this is much more spammy, but the only safe way. otherwise
   we might read over real variables' boundaries.
3) the string detection has been moved out of the size detection
   function, which better separates responsibilities of the 2
   funcs.